Turbine shroud assembly and method for loading

FIELD OF THE INVENTION

0001The present invention is directed to turbine components. More particularly, the present invention is directed to turbine components having an inner shroud loaded to an outer shroud.

BACKGROUND OF THE INVENTION

0002In gas turbines, certain components, such as the shroud surrounding the rotating components in the hot gas path of the combustor, are subjected to extreme temperatures, chemical environments and physical conditions. Inner shrouds are subjected to further mechanical stresses from pressures applied to load the inner shroud to the outer shroud, pushing against the pressure of the hot gas path. Pressurizing the space between the inner shroud and the outer shroud leaks high pressure fluid into the hot gas path, decreasing efficiency of the turbine. Further, mechanisms for mechanically loading the inner shroud against the outer shroud, such as springs, exhibit decreased effectiveness at high temperatures, and the springs themselves may creep over time, leading to insufficient loading pressure.

BRIEF DESCRIPTION OF THE INVENTION

0003In an exemplary embodiment, a turbine shroud assembly includes an inner shroud having a surface adjacent to a hot gas path, an outer shroud, and a biasing apparatus. The biasing apparatus is arranged and disposed to bias the inner shroud in a direction away from the hot gas path, loading the inner shroud to the outer shroud.

0004In another exemplary embodiment, a turbine shroud assembly includes an inner shroud having a surface adjacent to a hot gas path, an outer shroud, and a springless biasing apparatus. The springless biasing apparatus includes at least one bellows, at least one thrust piston, or a combination of at least one bellows and at least one thrust piston, and is arranged and disposed to bias the inner shroud in a direction away from the hot gas path, loading the inner shroud to the outer shroud.

0005In another exemplary embodiment, a method for loading a turbine shroud assembly includes biasing an inner shroud having a surface adjacent to a hot gas path in a direction away from the hot gas path toward an outer shroud. Biasing the inner shroud includes a biasing force exerted by a biasing apparatus.

0006Other features and advantages of the present invention will be apparent from the following more detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

0007<figref idref="DRAWINGS">FIG. 1</figref> is a sectioned view of turbine shroud assembly, according to an embodiment of the disclosure.

0008<figref idref="DRAWINGS">FIG. 2</figref> is a perspective view of the inner shroud of <figref idref="DRAWINGS">FIG. 1</figref>, according to an embodiment of the disclosure.

0009<figref idref="DRAWINGS">FIG. 3</figref> is a sectioned view of turbine shroud assembly, according to an embodiment of the disclosure.

0010Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.

DETAILED DESCRIPTION OF THE INVENTION

0011Provided is a turbine shroud assembly. Embodiments of the present disclosure, for example, in comparison to concepts failing to include one or more of the features disclosed herein, increase efficiency, increase durability, increase temperature tolerance, reduce the possibility of loss of load, reduce overall cost, and eliminate the need for pressurizing the shroud, produce other advantages, or a combination thereof.

0012Referring to <figref idref="DRAWINGS">FIG. 1</figref>, a turbine shroud assembly <b>100</b> includes an inner shroud <b>102</b>, an outer shroud <b>104</b>, and a biasing apparatus <b>106</b>. The inner shroud <b>102</b> includes a surface <b>108</b> adjacent to a hot gas path <b>110</b>. The biasing apparatus <b>106</b> is arranged and disposed to bias the inner shroud <b>102</b> in a direction <b>112</b> away from the hot gas path <b>110</b>, loading the inner shroud <b>102</b> against the outer shroud <b>104</b>. The biasing apparatus <b>106</b> may be connected to the inner shroud <b>102</b> by any suitable attachment, including, but not limited to, a pin <b>122</b>, a hook, a dovetail, a t-slot, or combinations thereof.

0013In one embodiment, the biasing apparatus <b>106</b> exerts a biasing force on the inner shroud <b>102</b> sufficient to dampen vibrations of the inner shroud <b>102</b> against the outer shroud <b>104</b>. Without being bound by theory, it is believed that the vibrations of the inner shroud <b>102</b> are caused in part by the varying pressure field resulting from buckets/blades rotating in close proximity to the inner shroud <b>102</b>. In another embodiment, contact between the inner shroud <b>102</b> and the outer shroud <b>104</b> reduces ingestion of hot gasses from the hot gas path <b>110</b> into the shroud assembly <b>100</b>.

0014In one embodiment, either or both of the inner shroud <b>102</b> and the outer shroud <b>104</b> includes a ceramic matrix composite, a metal, a monolithic material, or a combination thereof. As used herein, the term “ceramic matrix composite” includes, but is not limited to, carbon-fiber-reinforced carbon (C/C), carbon-fiber-reinforced silicon carbide (C/SiC), and silicon-carbide-fiber-reinforced silicon carbide (SiC/SiC).

0015In one embodiment, the surface <b>108</b> includes an environmental barrier coating (EBC) which protects the surface <b>108</b> from water vapor, heat, and other combustion gases. In another embodiment, the surface <b>108</b> includes a thermal barrier coating (TBC) which protects the surface <b>108</b> from heat. In yet another embodiment, at least one of the EBC and the TBC coats the exterior <b>130</b> of the inner shroud <b>102</b>, including both the surface <b>108</b> as well as the distal surface <b>132</b>.

0016In one embodiment, the turbine shroud assembly <b>100</b> includes a springless biasing apparatus <b>106</b>. As used herein, a “springless” biasing apparatus <b>106</b> is a biasing apparatus <b>106</b> in which the biasing force loading the inner shroud <b>102</b> against the outer shroud <b>104</b> is not generated by a spring. In certain embodiments, a springless biasing apparatus <b>106</b> may include a spring provided that any included spring does not generate a biasing force loading the inner shroud <b>102</b> against the outer shroud <b>104</b>.

0017In one embodiment, the biasing apparatus <b>106</b> is driven by a pressurized fluid <b>114</b>. The pressurized fluid <b>114</b> may be any fluid, including, but not limited to, air. Suitable sources for pressurized air include air from a gas turbine compressor.

0018In one embodiment, the biasing apparatus <b>106</b> includes at least one bellows <b>116</b>. In a further embodiment, the at least one bellows <b>116</b> includes a first end <b>118</b> attached to the outer shroud <b>104</b> and a second end <b>120</b> configured to expand away from the hot gas path <b>110</b> in response to an increased internal pressure within the at least one bellows <b>116</b>. The second end <b>120</b> of the at least one bellows <b>116</b> may be attached to at least one pin <b>122</b> which connects to at least one projection <b>124</b> of the inner shroud <b>102</b>. In one embodiment, the second end <b>120</b> is attached to the at least one pin <b>122</b> by a stanchion <b>126</b>.

0019Referring to <figref idref="DRAWINGS">FIG. 2</figref>, in one embodiment the at least one projection <b>124</b> of the inner shroud <b>102</b> includes an insertion aperture <b>200</b>. The insertion aperture <b>200</b> is arranged and disposed such that the at least one pin <b>122</b> may be inserted through the insertion aperture <b>200</b> to reversibly attach the inner shroud <b>102</b> to the second end <b>120</b>.

0020Referring again to <figref idref="DRAWINGS">FIG. 1</figref>, in one embodiment, the at least one bellows <b>116</b> hermetically caps a pressurized fluidic supply line <b>128</b>. As used herein, “hermetically caps” indicates that there is little or no leakage of pressurized fluid <b>114</b> from the region where the at least one bellows <b>116</b> joins with the pressurized fluidic supply line <b>128</b>, and that there is also little or no leakage of pressurized fluid <b>114</b> from the at least one bellows <b>116</b>.

0021Referring to <figref idref="DRAWINGS">FIG. 3</figref>, in another embodiment, the biasing apparatus <b>106</b> includes at least one thrust piston <b>300</b>. The at least one thrust piston <b>300</b> includes a piston head <b>302</b> and at least one piston seal <b>304</b>. The at least one thrust piston <b>300</b> is configured to urge stanchion <b>126</b> in a direction <b>112</b> away from the hot gas path <b>110</b> in response to an increased pressure from the pressurized fluid <b>114</b>. The piston head <b>302</b> may be attached to at least one pin <b>122</b> which connects to at least one projection <b>124</b> of the inner shroud <b>102</b>. In one embodiment, the piston head <b>302</b> is attached to the at least one pin <b>122</b> by a stanchion <b>126</b>.

0022In the embodiment shown in <figref idref="DRAWINGS">FIG. 3</figref>, the at least one thrust piston <b>300</b> includes a pressurized fluid seal <b>306</b> disposed between the piston head <b>302</b> and the at least one pin <b>122</b>. The pressurized fluid seal <b>306</b> reduces leakage of the pressurized fluid <b>114</b> to the hot gas path <b>110</b>. Without being bound by theory, it is believed that leakage from the pressurized fluid seal <b>306</b> is dependent on the pressure differential across the pressurized fluid seal <b>306</b>, the circumference of the pressurized fluid seal <b>306</b> and operational wear. In another embodiment, the pressurized fluid seal <b>306</b> includes at least one of a lubricant and a non-galling metal pair.

0023Referring to <figref idref="DRAWINGS">FIGS. 1 and 3</figref>, a method for loading a turbine shroud assembly <b>100</b> includes biasing the inner shroud <b>102</b> in a direction <b>112</b> away from the hot gas path <b>110</b> toward the outer shroud <b>104</b>, wherein biasing the inner shroud <b>102</b> includes a biasing force exerted by the biasing apparatus <b>106</b>. The biasing force is proportional to the pressure of the pressurized fluid <b>114</b>. In one embodiment, the pressurized fluid <b>114</b> is sourced at a fixed location in the gas turbine compressor, and the biasing force varies with the pressure generated by the gas turbine compressor. In another embodiment, the biasing force may be controlled by adjusting the pressure of the pressurized fluid <b>114</b>.

0024In one embodiment, loading a turbine shroud assembly <b>100</b> by biasing the inner shroud <b>102</b> in a direction <b>112</b> away from the hot gas path <b>110</b> toward the outer shroud <b>104</b> reduces damaging vibrations in the inner shroud <b>102</b>, in comparison to a turbine shroud assembly <b>100</b> in which the inner shroud <b>102</b> is biased in a direction toward the hot gas path <b>110</b> away from the outer shroud <b>104</b>. Without being bound by theory, it is believed that such damaging vibrations may be exacerbated in a turbine shroud assembly <b>100</b> in which the space between the inner shroud <b>102</b> and the outer shroud <b>104</b> is not pressurized by a fluid, such as, by way of example only, pressurized fluid <b>114</b>.

0025While the invention has been described with reference to one or more embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.